Transducer power supply for oscillators



J. F. WOOD TRANSDUCER POWER SUPPLY FOR OSCILLATORS March 8, 1960 2Sheets-Sheet 1 Filed Aug. 51, 1955 March 8, 1960 J. F. WOOD TRANSDUCERPOWER SUPPLY FOR OSCILLATORS 2 Sheets$heet 2 Filed Aug. 31, 1955 QQN2,928,052 Patented Mar.

TRANSDUCER POWER SUPPLY FOR OSCILLATORS John F. Wood, Buchanan, Mich.,assignor to Electro- Voice, Iucorporated,..Buchanan, Mich.

Application August 31, 1955, Serial No. 531,678

10 Claims. or. 331-185) I The present application relates to powersources, particularly to power sources for high impedance loads.

Devices have been developed in recent years which require relativelysmall amounts of power to operate them. On such device is thetransistor. Transistors operate on relatively low voltages and smallcurrent drains. For this reason, many transistor devices have beenconstructed which employ dry cell batteries to operate them. The batterylife in such'devices is essentially the same as the shelf life for thebatteries, however, batteries do have limited shelf lives, and hence, itis necessary to periodically replace the batteries used in such devices.Batteries also add considerably to the weight of the equipment, and alsoare relatively expensive. They are not sufiiciently reliable over longperiods of use. It is therefore one of the objects of the presentinvention to provide a power source which uses mechanical energy anddoes not require batteries.

The transistor has found application in signaling devices which areintended to be remotely operated for both civilian and militaryapplications. Some of the chief' advantages of transistors in remotesignaling devices are lightweight and small power requirements. It isone of the objects of the present invention to provide a power sourceoperating totally upon mechanical ener y which is especially adapted fora signaling device employing transistors.

I Another application for a high impedancepower source is in radiationmeasuring devices, particularly portable radiation measuring devices.Ionization chambers and counters require very little current foroperation, but do require substantial voltage. It is also very desirablethat a radiation'measuring device be capable of portable operation,sinceportable operation may be required to determine radioactivecontamination, as well asto prospect for uranium ore and otherradioactive substances.v It is therefore a further object of the presentinvention to provide a mechanically actuated power source particularlysuitable forum with radiation measuring devices.

These and other objects of the present invention will be more fullyunderstood when viewed in the light of the drawings, in which:

Figure 1 illustrates a signaling device having a power sourceconstructed according to the teachings of the present invention; 7

Figure 2 is a sectional view taken along the line 2--2 of the powersource illustrated in Figure 1;

Figure 3 is an elevationalview of another embodiment of the presentinvention illustrating a signaling device having a power source with afull wave rectifier;

Figure 4 is a sectional view along the line 4-4 of Figure 3; I

Figure 5 illustrates still another embodiment of the invention, aradiation measuring device being shown schematically and a portion ofthe power source being shown in section; and

Figure 6 is a sectional view taken along the line 6-6 QfFigure'S. e

The signaling device illustrated in Figures 1 and 2 has a' power source10 connected to an oscillator 12 which utilizes a transistor 14. I

The power source 10 utilizes a piezoelectric crystal 16 which is mountedto a support member 18 and extends with its axis normally disposedtherefrom. The crystal 16 is a bender type crystal cut in the form of atruncated plate, and the base 20 of the plate is rigidly secured to thesupport member 18. The parallel confronting sur faces of the plateshaped crystal 16 are provided with coatings 22 and 24 of electricallyconducting material, such as silver in the particular constructiondescribed herein. The crystal may be any piezoelectric material, suchasRochelle salt or barium titanate.

The surface of the crystal 16 opposite to the base, designated 26, issecured to an arm 28. The arm 28 .extends outwardly from the crystal 16and it is totally supported by the crystal 16. The arm 28 is constructedof resilient material, such as spring steel, orother ma terialssuitablefor vibrating reeds. A mounting member 30 which is provided with anindentation 32 is disposed between an arm 28 and crystal 16 with thecrystal 1 6 securely positioned within the indentation 32 of themounting member 3th The arm 28 is attached to the exterior surface ofthe mounting member 30, and the mounting member 39 is constructed ofelectrically insulated material when the arm 28 is constructed ofelectrically conducting material.

A pair of parallel confronting plates 34 and 36 extend outwardly fromthe support member 18 on opposite sides of the crystal 16 and parallelwith the surfaces thereof. The plates 34 and 36 are provided withconfronting apertures 38 and 4t and a pin 42 is translatably disposedwithin'the,apertures 38 and 49. The pin 42 is disposed normal to theconfronting surfaces of the crystal 16 and confronts the free end of thearm 28. A tooth, or catch 44, is secured to the pin 42 between theconfronting plates 36 and 38, and the catch 44 extends outwardly fromthe pin 42 in the direction of the crystal 16 a suflicient distance tocontact the free end of the arm 28 when translated toward it. The pin 42also has a restricted portion 46 extending from adjacent to the catchthrough tion 46 of the pin and has one end abutting the plate 38 and theother end abutting a shoulder 50 on the pin between the restrictedportion 46 and the expanded portion 47 of the pin 42. The pin 42 is alsoprovided with agroove 52 in the expanded portion 47 between the catch 44and the plate 34, and a C washer is secured within the groove 52 toprovide a stop against the plate 34.

The transistor 14 is a point or junction type transistor using a base56, emitter 58, and collector 6 0. The base- 56 is connected to one ofthe electrically conducting coatlugs 22 on the crystal 16 through acondenser 62 and resistor 64 connected in parallel. The emitter 58 ofthe transistor 14 is connected to the other coating 24 on the crystal 16through a resistor 66 and a rectifying diode 68 connected to passcurrent from the crystal 16 to theemitter 58. The emitter 58 is alsoconnected to the junction between a pair of condensers 7t and 72, thecondensers being connected to the ends of a tank coil 74. One end of thecoil 74 is also connected to the coating 22 on the crystal 16, whichform a ground terminal, and,

the other end of the coil 74 is connected directly to the collector 60of the transistor 14. A second coil 76 is coupled to the first coil 74,and one end of the coil 76 is connected to the ground terminal and theother end'to a radiating means 78.

' In order to place the signaling device into operation, it is onlynecessary to press the end of the pin 42 which extends through the plate34 toward the plate, thus translating the pin 42 and the catch 44 toabut the arm 28 and set the arm 28 into vibration. The vibration of thearm 28 causes the crystal 16 to generate voltages which appear asalternating charges upon the coatings 22 and 24. These charges areconducted to the oscillator 12 through the rectifying diode 68, thusenergizing the oscillator 12 and producing a signal with a resonant frequency of the tank circuit of the oscillator 12, which consists of thecoil 74 and the condensers 7t and 72. The signal produced is in the formof a series of pulses with a repetition rate equal to the vibrationfrequency of the crystal 16. In this manner, the transmitter 12 producesa signal which is amplitude modulated at the frequency of the arm 28.

The fact that the signal produced by the oscillator 12 is amplitudemodulated makes it possible to operate a sensitive circuit by means offilters tuned to the modulation frequency of the signal, and thus keythe oscillator 12 to the sensitive circuit. Also a plurality oftransducers 10 may be connected in series and used to energize theoscillator 12, thus amplitude modulating the oscillator with a pluralityof frequencies. A receiving circuit may then be keyed to each of thesefrequencies.

The transmitter 12 also will produce an unmodulated carrier if acondenser 86, illustrated in dotted lines in Figure l, is connectedbetween the junction of the resistor 66 and the rectifying diode 68 andthe ground terminal of the oscillator 12. The voltage pulses appearingacross the output of the diode 68 are then stored by the condenser 80,thus supplying a constant direct current to the oscillator 12. I Theoscillator 12 will continue to produce a signal until the amplitude ofthe vibrations of the arm 28 falls sufficiently to reduce the voltagedeveloped by the crystal 16 to a value insuificient to excite theoscillator 12. The operator must then again depress the pin 42 into theplate 34, and upon releasing the pin, the spring 48 will again drive thecatch 44 across the end of the arm 28, and renew its vibrating energy.The maximum voltage output of this power supply is limited principallyby the breaking strength of the crystal 16.

Figures 3 and 4 illustrate a full wave rectified power supply incombination with an oscillator 101, which may be identical with theoscillator 12 shown in Figure 1. In this device, a pair of parallelplates 182 and 104 are attached normal to a plate shaped support member106. The plates 102 and 104 are provided with apertures 106 and 108, andanaxle 110 is rotatably journaled within the apertures 106 and 188. Acrank handle 112 is at tached to the end of the axle 110, adjacent tothe plate 104. A wheel 114 is secured to the axle 110 centrally betweenthe plates 102 and 104. The wheel 114 is provided with a plurality ofspaced protruding teeth 116.

An electromechanical transducer 118 is mounted to the support member 106confronting the wheel 114. This transducer 118 has a pair ofpiezoelectric crystals 120 and 122 which are mounted together to form abender type crystal. Each of the crystals 120 and 122 are plate shaped,and one of the surfaces of each crystal is bound together by a commonelectrically conducting coating 124, thus forming a crystal which bendsrather than twists. The other surface of crystal 120 is provided with anelectrically conducting coating 126, and the other surface of thecrystal 122 is also provided with an electrically conducting coating128. An arm 13!) is attached to the end of the crystals 120 and 122opposite to the support member 182 by a mounting member 132. Themounting member 132 is provided with an indentation 133 into which theelectromechanical transducer 118 is disposed and secured, and the arm130 is attached to the mounting member 132 to be disposed parallel tothe surface of the crystals 120 and 122.. The arm 1 i constructed ofresilient material, such as spring steel, and the mounting member 132 isconstructed of electrically insulating material, such as plastic. Thearm extends away from the electromechanical transducer 118 and confrontsthe wheel 114, so that the teeth 116 thereof will abut the arm 130 whenthe wheel is rotated by the crank 112.

The electrically conducting coating 126 of the crystal 120 iselectrically connected to a rectifying diode 134, and the electricallyconducting coating 128 of the crystal 122 is electrically connected to arectifying diode 135. The output sides of the diodes 134 and areinterconnected. The coating 124 common to both crystals 120 and 122 isconnected to the ground terminal of the oscillator 101, and a condenser136 is connected between this terminal and the interconnected terminalsof the diodes 134 and 135.

Since the surfaces 126 and 128 of the crystals 12d and 122 developpotentials of opposite sign when the crystals are bent to eitherdirection, an alternating current is developed equal in voltageamplitude to the sum of the voltage developed by each crystal. Thealternating current generated by the crystals 120 and 122 is conductedthrough the diode rectifiers 134 and 135 to produce a direct currentcharge on condenser 136.

In order to excite the oscillator 12, the crank handle 112 is rotated,causing the teeth of the wheel 114 to contact the arm 130 and set itinto vibratory motion. Since the amplitude and the vibrations of the arm130 are restored each time the arm 130 is released by one of the teeth116 of the wheel 114, the direct current voltage supplied to theoscillator 12 remains substantially constant. The principal effect ofthe condenser 136 is to provide a storage of charge to compensate forthe dropping off of the voltage generation of the electro mechanicaltransducer 118 during the portion of the cycle in which the arm 130 isin actual contact with one of the teeth 116 of the wheel 114, sinceduring this period of time very little voltage generation will occur.The condenser 136 also eliminates hum. I

Figures 5 and 6 illustrate another embodiment of the present inventionwhich utilizes an electromagnetic power source in combination with aradiation measuring device.- The power source, designated 150, utilizesa support plate 152 upon which a bar magnet 154 is mounted. The magnet154 is provided with pole pieces 156 and 158 which extend away from thesupport plate 152 through the ends of the magnet 154 and are thenprovided with bends 159 toward each other, thus forming a gap 160. Acoil 162 consisting of a plurality of layers of turns is disposedbetween the pole pieces 156 and 158 and rests upon the magnet 154.

A pair of support members 164 and 166 extend outwardly from the supportplate 152 and are provided with confronting apertures 168 and 170. A pin172 is translatably disposed within the apertures 168 and 170, and thepin 172 is provided with a protruding catch 174 centrally thereof. Aresilient arm 176 constructed of material having high magneticpermeability is secured at one end to the center of the bar magnet 154,and the arm 176 extends through the gap to confront the pin 172. Thecatch 174 is adapted to abut the arm 176. The arm 176 is constructed ofmaterial of high resilience and permeability, so that the arm 176 isplaced in vibration when the catch 174 displaces and releases the armfrom its position of rest.

The pin 172 has an enlarged portion 177 and a restricted portion 178which is rectangular in shape, the aperture through which the restrictedportion 178 is slightly disposed also being rectangular in shape andrestricting rotation of the pin 172. A helical spring 180 is disposedabout the restricted portion 178 of the pin 172 and abuts against thesupport plate 166 and a shoulder 182 between the restricted portion 178and enlarged portion 176 of the pin L 12! The pin .172 is 174 and theplate 164 anda- C type washer 184 is securedwithin the groove 183 toprovide a stop for the pih172against the plate 164. When the enlargedportion 177 of the pin 172 is V electromagnetic power source illustratedin Figures pushed toward the plate 164 the catch 174 will engage the arm176 and then release the arm 176 placing it in As a result analternating magvibratory resonance. n'e'tic flux will flow in a pathfollowing the arm 176, the pole pieces 156 and 158 and the magnet 154.In this manner, the alternating'magnetic flux induces a voltage in thecoil 162 which is alternating in form.

The radiation measuring device utilizes a counting chamber 190 connectedin a series circuit consisting of the ehamber 190, a condenser 192 and aresistor 194. A crystal type head set-196 is connected in parallel withthe resistor 194 to give an audible indication of a voltage pulsedeveloped across the resistor 194. The junction of resistor 194 andcondenser 192 is directly connected to'one end of the coil 162 of thepower source 150 and the other end of the coil 162 is also connected tothis junction through a condenser 198 and a rectifying diode 200. Thejunction between the condenser 198 and rectifying diode 200 is alsoconnected to the junction of condenser 192 and resistor 194 through adiode 202 and a condenser 204 and the junction between the diode 202 andcondenser 204 is again connected to the junction of condenser. 192 andresistor 194 through a resistor 206 and gaseous voltage regulating tube208 The junction between resistor 206 and the voltage regulating tube208 is connected to the junction between the ionization chamber 190 andthe condenser 192 through a resistor 210.

The alternating voltage developed by the power source 150 is rectifiedand multiplied by condenser 198, diode 200,'diode 202 and condenser 204,since these elements are connected in a conventional circuit for thesepurposes. Itis to be understood'that the voltage multiplier circuit isnot absolutely necessary and may be eliminated if the coil 162 hassuflicient turns to generate a high enough potential. The use of avoltage multiplier circuit, however, permits a smaller coil 162, andhence a more efiicient magnetic circuit. The voltage multiplier could ofcourse employ more than two diodes in a conventional circuit, thuspermitting use of an even smaller coil 162.

The voltage developed across condenser 204 is approximately twice thatdeveloped across the coil 162, and this voltage is applied to thecounting chamber 190 through the voltage regulating circuit consistingof re sistors 206 and 210, and voltage regulator tube 208, therebyplacing a potential on the chamber 190 within the proper range. Whenradiation impinges upon the counter chamber 190, it causes current toflow through the counter circuit consisting of the counter 190,condenser 192 and resistor 184. This develops a voltage across resistor194 which is audible in the form of a pulse in the crystal head set 196.

In all of the embodiments of the invention herein disclosed, anelectromechanical transducer is used to develop electrical energy frommechanical energy. The mechanical energy required is vibratory in eachcase, and the transducer responds to this mechanical energy when thevibration occurs in at least one plane, referred to as the responsiveplane of the transducer.

The man skilled in the art will readily devise many modifications of thepresent invention and many uses for the present invention in addition tothose described. For example, it is obvious that the piezoelectric powersource, illustrated in Figures 1 and 2, or in Figures 3 and 4, could besubstituted for the electromagnetic embodiment of the inventionillustrated in Figures 5 and 6, and vice versa. Further, it is obvious,that the toothed wheel illustrated in Figures 3 and 4 could be employedin the powersource shown in Figures 1 and 2 or the and '6. Further, thepiezoelectric power source of Figures 1 and 2 and Figures 3 and 4utilize crystals which generate a voltage by bending, while it isobvious that crystals generating potentials by twisting could beemployed. For these reasons, it isintended' that the scope of thepresent invention be not limited to the foregoing disclosure, but ratheronly by the appended claims.

' The invention claimed is:

1. A power source comprising an electromechanical transducer respondingto'vibratory motion in at least one plane, a flexible arm secured to thetransducer, and

means to set the arm into vibrating motion comprising a support meanssecured to the transducer, and a pin reciprocally mounted to the supportmeans generally parallel to the responsive. plane of the transducer;-said pin having a tooth extending outwardly therefrom confront ing thearm, whereby reciprocation of the pin causes the tooth to contact thearm, bend the arm, and release the arm, thus setting the arm intovibratory motion. I

2. A power source comprising an electromechanicaltransducer respondingto vibratory motion in at least one plane, a flexible arm secured to thetransducer, and means to set the arm into vibratory motion comprising asupport means secured to the transducer including a pair of parallelplates having confronting apertures therein, said apertures beingdisposed on an axis generally parallel to the responsive plane of thetransducer, and

a pin reciprocally disposed within the apertures in the plates, said pinhaving an outwardly extending tooth confronting the arm, wherebyreciprocation of the-pin causes the tooth to contact the arm, bend thearm, and release the arm, thus setting the arm into-vibratory motion.

3. A power source comprising an electromechanical transducer respondingto vibratory motion in at least one plane, a flexible arm secured to thetransducer, and means to set the arm into vibratorymotion com prising asupport means secured to the transducer including a'pair of parallelplates having confronting apertures therein, said apertures being on anaxis generally parallel to the responsive plane of the transducer, a pinreciprocally disposed within the apertures in the plates, said pinhaving an outwardly extending tooth confronting the arm and a protrudingstop between the tooth and the first of said plates adapted to abut saidplate, and a helical spring disposed about the pin, the end of saidspring adjacent to the tooth being secured to the pin betwen the toothand the second of said plates and the other end of said spring abuttingthe second of said plates, whereby reciprocation of the pin causes thetooth to contact the arrn, bend the arm, and release the arm, thussetting the arm into vibratory motion.

4. A power source comprising an electromechanical transducer respondingto vibratory motion in at least one plane, a flexible arm secured to thetransducer, and means to set the arm into vibratory motion comprising asupport means secured to the transducer having a pair of parallel platesprovided with confronting apertures therein, the aperture in the firstof said plates being larger than the aperture in the second of saidplates and said apertures being on an axis generally parallel to theresponsive plane of the transducer, a pin provided with a largerportion, a smaller portion and a shoulder therebetween reciprocallydisposed within the apertures in the plates, the larger portion beingsnugly disposed within the larger aperture and the smaller portion beingsnugly disposed within the smaller aperture, said pin having anoutwardly extending tooth confronting the arm and a transverse groovedisposed between the tooth and the first plate, a C-type washer disposedwithin said groove adapted to form a stop against the first plate, and ahelical spring disposed about the smaller portion of the pin, one end ofsaid pin abutting the shoulder of the pin and the other end abutting thesecond of said plates, whereby reciprocation of the pin causes the toothto contact the arm, bend the arm, and release the arm, thus setting thearm into vibratory motion.

5. A, power source for a high impedance load comprising the elements ofclaim 4 wherein the electromechanical transducer comprises apiezoelectric crystal mounted at one end generally normal to the pin andhaving electrically conducting coatings on confronting surfaces, the armbeing secured to the other end of the crystal.

6. A power source for a high impedance load comprising the elements ofclaim 1 wherein the electromechanical transducer comprises apiezoelectric crystal mounted at one end generally normal to themoveable member and having electrically conducting coatings onconfronting surfaces, the arm being secured to the other end of thecrystal.

7. A power source comprising the elements of claim 1 wherein theelectromechanical transducer comprises a support member, a magnetmounted to the support member, a pair of pole pieces attached to themagnet at one end and forming a gap at the other end, the flexible armbeing constructed of magnetically permeable material and mounted to themagnet at one end, said arm extending through the gap adjacent to itsother end, and a coil disposed about the arm.

8. A power source comprising the elements of claim 3 wherein theelectromechanical transducer comprises a magnet mounted to the supportmember, a pair of pole pieces attached to the magnet at one end forminga gap at the other end, the flexible arm being constructed ofmagnetically permeable material and mounted to the magnet at one end,said arm extending through the gap adjacent to its other end, and a coildisposed about the arm.

9. A power source comprising the elements of claim 1 wherein theelectromechanical transducer comprises a first plate shapedpiezoelectric crystal having electrically conductive coatings onconfronting faces, a second plate shaped piezoelectric crystal havingelectrically conducting coatings on confronting faces, means to securetwo of said faces together to form a common terminal, said crystalsbeing mounted to the support means at one end and the flexible arm beingsecured to the other end of said crystals.

10. A signaling device comprising an oscillator having a transistor, aresonant tank circuit electrically connected to the transistor, and apower source electrically connected to the transistor characterized bythe construction wherein the power source comprises an electromechanicaltransducer responding to vibratory motion in at least one plane, aflexible arm secured to the transducer, means to set the arm intovibratory motion comprising a support means secured to the transducerincluding a pair of parallel plates having confronting apertures thereindisposed on an axis generally parallel to the responsive plane of thetransducer, and a pin reciprocally disposed within the apertures of theplates, said pin having an outwardly extending tooth confronting thearm, and a rectifier connected between the electromechanical transducerand the transistor.

References Cited in the file of this patent UNITED STATES PATENTS

